The one was a picture of a large number of crosses which Trump said was a burial site for 1000s of white farmers, when it was in fact a memorial following the death of 2 farmers. The memorial was intended to represent all farm deaths of all races. Farm deaths are an issue but the victims are of all races - they kill the farmers, their families and the workers.
There was a video of a political leader singing a song that translates to “Kill the Boer” i.e. kill the white Afrikaans farmer. This video is: a) more than a decade old, b) from a rally of a minority opposition party i.e. not the political party of the people Trump was meeting, c) from a political party that has been losing votes in recent elections, led by someone who was expelled from the ruling party, d) is of a historic protest song from the apartheid era i.e. more than 30 years ago.
This video resulted in a court case, where the court concluded that a “reasonably well-informed person” would understand that when a protest song is sung “even by politicians, the words are not meant to be understood literally, nor is the gesture of shooting to be understood as a call to arms or violence.”
This video was a big deal at the time but it’s not current, not representative of the government’s view, and the person depicted in it is increasingly being sidelined in South African politics.
As I said, the song was a really big deal when it happened, there was a massive outcry. I believe the incident took place in 2013, the year Malema founded his party. His platform absolutely runs on hatred of white people, and this was a way for him to gain political relevance.
The objections to Malema singing the song went through the courts, as they should, and Malema had to go all the way to the Supreme Court of Appeal. (The final judgement is from 2024.) I would assume that he sang it again after that but honestly try to ignore him as much as possible.
However, there was no point in Trump showing videos of Malema to the South African delegation. They had nothing to do with it. In fact, the ANC promised in 2012 never to sing that protest song again (it was originally one of their protest songs).
More importantly, this video is not evidence of a white genocide, past, present, or planned.
Edit to add: The reality is that there is a notable segment of the population that is angry. The economy is bad, unemployment is crazy high, electricity is insufficient (load shedding is a disaster), violent crime remains high, etc. It’s easier for them to keep blaming white people than acknowledge that it’s been 30 years of black rule now. Malema is a symptom of these issues. A meaningful discussion around this topic would have been valuable, but that’s not what Trump did.